Wearable absorbent articles (e.g., taped diapers, pull-on diapers, training pants, incontinence briefs) offer the benefit of receiving and containing urine and/or other bodily exudates of a wearer. Wearable absorbent articles typically include an absorbent core assembly for storing the bodily exudates positioned between a liquid pervious topsheet and a liquid impermeable backsheet. While such absorbent articles may be suitable for meeting a basic need of exudate containment, some wearers of disposable absorbent articles and/or the caregivers of such wearers may desire a disposable absorbent article that provides increased comfort to the wearer and/or is more aesthetically pleasing, for example, by including features typically associated with cotton underwear.
Cotton underwear generally includes cotton fibers suitable for making soft, relatively strong material (i.e., cloth). Cotton underwear is typically configured to exhibit low-force stretch and good recovery (i.e., the material is extensible when a relatively low amount of force is applied and returns substantially to its prestrain shape/size when the force is removed), especially in the waist regions of the underwear, which are typically required to stretch laterally across the upper pelvic, lower abdominal, and/or upper buttocks regions of a wearer, when the wearer is physically active (e.g., walking, running, and/or crawling). In addition to stretchable waist regions, cotton underwear may also include elastic waist and/or leg bands. The elastic waist and/or leg bands may encircle the waist and/or legs of the wearer to provide 360-degree stretch around the waist and/or legs. Unlike some disposable articles, however, cotton underwear is typically not designed to accommodate large discharges of bodily waste from wearers. Additionally, cotton underwear is generally not used as a “disposable” article (i.e., intended to be discarded after relatively few uses rather than laundered and reused). Further, cotton underwear tends to be more expensive than a disposable diaper.
Despite the problems that may be associated with cotton underwear, at least some manufacturers of disposable absorbent articles desire to provide a disposable absorbent article that includes one or more of the desirable features of cotton underwear. To this end, the manufacturer may include an outer cover on the disposable article that is formed from a material having the look and feel of cloth. The manufacturer may also form the outer cover to have elastic properties similar to those of underwear. For example, it is known in the art that an extensible polyethylene-containing nonwoven may be joined with an elastic material (e.g., nonwoven, film, or strand) to form an elastic laminate, and then subjected to an activation process (sometimes referred to as incremental stretching). The extensible polyethylene-containing nonwoven is typically used to provide the desired softness to the laminate. After the laminate is subjected to a suitable activation process, the elastic material may be capable of providing the desired elasticity. Examples of elastic laminates include “zero-strain” stretch laminates (i.e., laminates formed by joining an extensible nonwoven to an untensioned elastic material and then subjecting the laminate to an activation process), stretch-bonded laminates, and necked-bonded laminates.
Examples of stretchable laminates and methods for making stretchable laminates may be found in: U.S. Pat. No. 4,116,892, titled “Process for Stretching Incremental Portions of an Orientable Thermoplastic Substrate and Product Thereof,” to Schwarz; U.S. Pat. No. 4,834,741, titled “Diaper With Waistband Elastic,” to Sabee; U.S. Pat. No. 5,156,793, titled “Method for Incrementally Stretching Zero Strain Stretch Laminate Sheet In A Non-Uniform Manner To Impart A Varying Degree Of Elasticity Thereto,” to Buell et al.; U.S. Pat. No. 5,167,897, titled “Method for Incrementally Stretching A Zero Strain Stretch Laminate Sheet To Impart Elasticity Thereto,” to Webber et al.; and U.S. Pat. No. 5,422,172, titled “Elastic Laminated Sheet of An Incrementally Stretched Nonwoven Fibrous Sheet and Elastomeric Film and Method,” to Wu. However, polyethylene-containing nonwovens may not provide a suitable amount of material strength, or bond strength when joined to other absorbent article components. In addition, certain processes used to form outer covers for disposable absorbent articles may cause polyethylene-containing nonwovens to produce fuzz on the surface of the outer cover, which some users may find undesirable.
Another feature that manufacturers of disposable absorbent articles may include on a disposable absorbent article to make it more underwear-like is an elastic leg and/or waist opening configured to provide 360-degree stretch around the leg or waist of a wearer. The elastic leg and/or waist opening, when coupled with a cloth-like outer cover on a disposable absorbent article, may provide an article with, e.g., reduced gapping between the absorbent article and the leg of the wearer and/or improved containment of exudates stored in the disposable absorbent article. The elastic material used to form a leg and/or waist opening may be joined to an activated portion of a nonwoven outer cover so that the soft, cloth-like material to which the leg band is joined does not impede or “lock up” the stretchability of the elastic leg band (i.e., inhibit the leg band from stretching over its full range). In this way, the leg opening of the disposable absorbent article can extend further than the “virgin” (i.e., unactivated) nonwoven material, and thereby fit a wider range of wearer leg sizes than some traditional leg opening configurations. However, due to the tradeoff between unactivated and activated material properties (e.g., opacity versus strength), some manufacturers of disposable absorbent articles may limit how much of the leg opening portion of the outer cover is activated (e.g., how far the activated portion extends laterally inward). If the leg band is positioned too close to the nonactivated leg opening portion of the outer cover or if the activated portion of the outer cover is too narrow (relative to the width of the leg band), the extensibility of the leg opening may still be restricted, resulting in an undesirable fit in the leg opening area of the disposable absorbent article.
Activating an extensible material typically subjects portions of the material to relatively high strain and/or strain rates, which may result in undesirable changes to the thickness, opacity, strength, and/or other physical properties of the material. Insufficient opacity may result in the undesirable visibility of the wearer's skin or bodily exudates stored in the absorbent article, and insufficient strength may result in the finger of a caregiver or foot of a wearer penetrating one or more layers of the outer cover (i.e., “poke-through”). In addition, certain materials that provide a desirable amount of softness such as polyethylene-containing nonwovens may not have a suitable level of strength. On the other hand, certain materials that provide a desirable level of strength such as polypropylene nonwovens may not provide a suitable amount of softness. Including an elastomeric material in the outer cover of an underwear-like absorbent article may reduce at least some of the undesirable effects related to activation by providing increased opacity, decreased “set” (i.e., permanent deformation resulting when a material is extended, then allowed to relax) induced by the activation process, and/or structural strength (e.g., in areas of the article where the nonwoven may have been weakened by the activation process). However, elastomeric film materials tend to be relatively expensive compared to the nonwoven materials typically used in absorbent article outer covers. Therefore, the elastomeric film material may be present only in areas of the outer cover where elasticity is most desired (e.g., waist regions and/or leg band regions) as opposed to including a full-length elastomeric film material. The absence of an elastomeric film in the leg band region of the outer cover may require a reduction in the amount of activation in this area (e.g., reduced depth of engagement of the intermeshing teeth of the activation apparatus) to maintain a desirable level of material strength or integrity. Reducing the amount of activation, however, may result in an increase in the amount of force required to stretch the leg band region of the outer cover to fit the desired range of wearer sizes, which may further reduce the range of wearer sizes.
One way to address the problems of low opacity and/or strength is to include one or more additional full-coverage (i.e., length and width) layers of nonwoven material to the outer cover and/or increase the basis weight of the single, full-coverage layer of nonwoven material. The additional full-coverage layer(s) of nonwoven and/or higher basis weight nonwovens may overcome at least some of the problems associated with low opacity and low strength and may even be cheaper than a full-coverage elastic film. However, there may still be an undesirable increase in the cost of producing the outer cover. In addition, some disposable absorbent articles may include graphics and other indicia on the outer cover (e.g., popular cartoon characters, letters, numbers, and/or shapes), which are commonly printed or embossed onto the inner and/or outer facing surface of the outer cover. The additional layers of nonwoven and/or higher basis weight material in the outer cover may undesirably obscure the graphics (e.g., the graphics may be distorted and/or less vibrant).
Another problem that may be encountered when providing a cloth-like, stretchable outer cover for a disposable absorbent article is that the properties (e.g., thermal and/or chemical) of the various outer cover components may not complement each other or even be compatible. For example, in order to provide a suitable cloth-like outer cover it may be desirable to securely join leg bands to the outer cover. The leg bands may be made from a material that provides good softness (e.g., polyethylene based). However, it may be undesirable to fabricate the entire outer cover from polyethylene due to cost or other factors. In this instance, the leg band and the outer cover may be formed from different materials that impart desired properties to each component of the absorbent article. Due to the different chemical/thermal properties of the outer cover material and the leg band material, suitable bonds (e.g., high pressure or thermal bonds) may not be formed between the leg band and the outer cover, potentially resulting in a poor quality absorbent article. Thus, it may be problematic to directly couple various absorbent article components to one another due to the differences in the chemical and/or thermal properties of the outer cover and component materials.
Accordingly, it would be desirable to provide a reduced cost disposable absorbent article with the look and feel of cotton underwear. It would also be desirable to provide an outer cover with improved structural integrity and opacity in the crotch region. It would further be desirable to provide an absorbent article that has an outer cover with relatively unobscured graphics. It would additionally be desirable to decouple the bond strength of components bonded the outer cover from the chemistry of the outer cover material.